Light emitting diode driver

A driver circuit for driving light emitting diodes (LEDs), comprising:

• a string of LEDs divided into n groups, the n groups of LEDs being electrically connected to each other in series, a downstream end of group m−1 being electrically connected to the upstream end of group m, where m being a positive number equal to or less than n, an upstream end of group 1 being configured to be coupled to a power source that provides an input voltage;
• a plurality of current regulating circuits, each of the current regulating circuits being coupled to the downstream end of a corresponding group at one end and coupled to a ground at an other end and including a sensor amplifier and a cascode having first and second transistors, each of the current regulating circuits being coupled to a different reference voltage source;
• and
• a phase control logic for sending a signal to each of the current regulating circuits to thereby control a current flow through each of the current regulating circuits.